Apparatus for processing a control command sequence as well as a method for generating a control command sequence, and a storage medium for storing a control command sequence.
The invention relates to an apparatus for processing a sequence of control commands for a unit to be controlled as well as a method for generating a sequence of control commands for a unit to be controlled, and a storage medium for storing a sequence of control commands of a unit to be controlled.
The invention is based on an apparatus for processing a sequence of control commands for a unit to be controlled of the generic type of the independent claim 1. Such an apparatus has recently become known by virtue of the fact that the DVD (Digital Versatile Disc) playback devices that are the latest additions to the market have a so-called sub-picture decoding unit (sub-picture decoder). These sub-picture decoding units are designed according to the specification described in the DVD Standard (Version 1.0). A specific command set for control commands for driving the display unit is described and agreed in the DVD Standard (Version 1.0). The control commands and, if appropriate, video data are stored in a sub-picture unit. However, only very few control commands for the display control are provided in the current DVD standard. It may therefore be expected that in future DVD standardization proposals with version numbers greater than 1.0, additional control commands which are not yet contained in the current DVD standard (version 1.0) will be defined in order to make the display control even more convenient. If a sequence of control commands in which newly defined control commands also occur is therefore stored on storage media, for example the DVD disk, then the problem that currently exists is that such control command sequences cannot be processed in a compatible manner by a DVD playback device which has been developed according to today""s standardization proposal.
The aim of the invention is to take account of the above-described problem today, at an early stage, and, on the one hand, to design new playback devices in such a way that they can process the new control commands without any problems and, on the other hand, to arrange the new control commands in a sub-picture unit in such a way that even the playback devices which are designed according to the current DVD standard (Version 1.0) can decode the sub-picture unit having new control commands, without entering into an undefined state.
The object with regard to the new playback devices is achieved according to the invention by means of the measures specified in claim 1. The invention provides an apparatus for processing a sequence of control commands for a unit to be controlled, which is equipped with first decoding means for the control commands that have already been defined today, and which is additionally distinguished by the fact that the first decoding means (22) are designed in such a way that when a first end command (CMD_END) is processed, they carry out a comparison of the address of the end command (CMD_END) with an address information item regarding the start address (SP_NXT_DCSQ_SA) of the next control command sequence (SP_DCSQ1, SP_DCSQ2) and identify, from the difference between the addresses, whether the first end command is additionally followed by at least one further control command (SET_BAREA) which is selected from a second set of control commands (SET_BAREA). In addition, the apparatus has further decoding means which are designed in such a way that they can process the new control commands.
These measures have the advantage that the new playback devices can process the control command sequence including the newly defined control commands without any problems.
Advantageous developments and improvements of the apparatus specified in Claim 1 are possible by virtue of the measures evinced in claims 2-9. Thus, for example, it is very advantageous if, in the case where a next sequence of control commands is not provided, the address information item regarding the start address of the next control command sequence points to the beginning of the last sequence of control commands and then, when the address information item regarding the start address of the next control command sequence is decoded following the decoding of the further end command, the control of the unit to be controlled is set or the last sequence of control commands is repeated. If no abort criterion is provided for the resultant loop, then an endless loop is created which can be interrupted by external intervention.
If the last control command sequence is being processed, the address information item regarding the start address of the next control command sequence points to the beginning of the last control command sequence. It is then advantageous if the first decoding means are designed in such a way that they check whether the address of the first end command is the last or penultimate address of the control program unit, and that if the address is not the last or penultimate address, it is identified that at least one further control command will follow after the decoded end command and be processed by the further decoding means. The abovementioned sub-picture unit is cited as an example of the control program unit. These measures ensure that additional commands may be contained in the last control command sequence, too, and are able to be processed reliably by an appropriately designed playback device.
Display control commands come into consideration as control command and are then provided for the control of a display unit. On the other hand, the control commands may also relate to printer control commands or control commands for other units.
The second part of the object of the invention is achieved by the method for generating a sequence of control commands for a unit to be controlled in accordance with claim 10. It is advantageous for such a method if the sequence of control commands has first control commands which, as it were, correspond to the control commands already defined today, and additionally has second control commands which correspond to the extended control commands, the second control commands being arranged in combination after the known, first control commands in the sequence and being separated from the first control commands by an end command. The result achieved by this is that the conventional playback devices ignore the new control commands without entering into an undefined state. As a result of the characteristic of conventional playback devices whereby when an end command is decoded, they read out an address information item on the beginning of the control command sequence and begin the processing of the next control command sequence at the location specified by the address information item, these playback devices will ignore the additional control commands arranged after the end command and, therefore, will not enter into an undefined state. Undefined behaviour of the DVD playback devices designed according to the DVD standard (Version 1.0) is avoided.
The generated sequence of control commands is advantageously stored on a storage medium. A storage disk or a magnetic tape comes into particular consideration for this purpose.
The control commands are then advantageously stored sequentially one after the other on such a storage medium. Firstly, the known control commands should follow one after the other and then they should be followed by the new or further control commands. At the same time, the new control commands should be separated from the conventional control commands by an end command.